The present invention relates to a method of forming a tobacco bead on a cigarette manufacturing machine.
Cigarette manufacturing machines normally comprise a tobacco bead forming unit, in turn comprising a forming conveyor for conveying a tobacco bead at a given linear speed; a pressing device for compacting portions, equally spaced with a given spacing, of the tobacco bead conveyed on the forming conveyor; and a shaving device coordinated with the forming conveyor to remove a surplus tobacco portion off the tobacco bead conveyed on the forming conveyor.
To keep the mass of tobacco per unit of length of the tobacco bead within a given acceptance range alongside variations in the humidity of the tobacco and in the speed of the forming conveyor, the distance between the shaving device and the forming conveyor is regulated continuously by keeping the forming conveyor fixed and moving the shaving device vertically, or vice versa.
The function of the pressing device is to form denser portions along the tobacco bead, at the points corresponding to the tips of the cigarettes produced from the bead.
Known pressing devices have been found to have a tendency to produce uneven denser portions along the tobacco bead, which has a negative effect on the overall quality of the cigarettes produced from the bead, by introducing a dispersion factor into the functional characteristics of the cigarettes.
It is an object of the present invention to provide a method of forming a tobacco bead, designed to eliminate the aforementioned drawbacks, and which at the same time is straightforward and cheap to implement.
According to the present invention, there is provided a method of forming a tobacco bead by means of a forming conveyor for conveying a tobacco bead; a pressing device for compacting portions, equally spaced with a given spacing, of the tobacco bead conveyed on the forming conveyor; and a shaving device coordinated with the forming conveyor and for removing a surplus tobacco portion off the tobacco bead; the method providing for regulating a first distance between said shaving device and said forming conveyor as a function of the characteristics of the tobacco bead; and the method being characterized by estimating a linear travelling speed of the forming conveyor, and regulating a second distance between said pressing device and said forming conveyor as a function of said linear travelling speed of the forming conveyor.
The present invention also relates to a unit for forming a tobacco bead.
According to the present invention, there is provided a unit for forming a tobacco bead, the unit comprising a forming conveyor for conveying a tobacco bead at a given linear speed; a pressing device for compacting portions, equally spaced with a given spacing, of the tobacco bead; a shaving device coordinated with said forming conveyor and for removing a surplus tobacco portion off the tobacco bead; and first regulating means for regulating a first distance between the shaving device and the forming conveyor as a function of the characteristics of the tobacco bead; and the unit being characterized by comprising second regulating means for regulating a second distance between the pressing device and the forming conveyor substantially independently with respect to regulation of the first distance.